The present invention relates to a system for optimizing the operation of a marine drive unit and, more particularly, to a system for automatically returning a drive unit to a predetermined optimal position for any one of several conventional operating positions.
The drive units for marine propulsion devices, including outboard motors and stern drives, are typically supported from the boat transom by a drive mounting assembly. Various types of drive mounting assemblies are known, as for example a transom bracket for mounting an outboard motor directly on a boat transom or a gimbal ring assembly for similarly mounting a stern drive unit directly to the transom. A drive unit mounted directly on the boat transom may be trimmed by pivoting it about a generally horizontal axis in order to position the propellor and optimize thrust with respect to the plane of the boat. However, the vertical position of a drive unit mounted directly on the boat transom usually cannot be changed beyond the somewhat limited amount which inherently results from a trimming operation. Therefore, such a drive unit must typically be mounted in a compromise position at a fixed height with respect to the transom which will provide the best overall performance. Another type of drive mounting assembly is one which is capable of selectively supporting an outboard motor in either a raised or lowered position aft of the boat transom. Many of these so-called "transom extension" mounting assemblies are of the general type which include a pivotally connected quadrilateral linkage, generally in the form of a parallelogram.
Transom extension mounting assemblies have become increasingly popular on high performance and fishing boats powered by outboard motors where a lower position of the motor improves initial boat acceleration and a higher position enhances cruising speed by reducing gear case drag. Additionally, a higher motor position reduces draft, thereby enhancing shallow water and/or trolling operation. It is further known that relocating the motor aft of the transom improves the high speed handling characteristics of most boats.
Transom extension mounting assemblies which utilize a quadrilateral linkage arrangement cause the motor to be raised or lowered with respect to the boat by controlled collapse of the linkage via a powered operating system. A separate powered operating system is usually used to provide trim movement to the motor. The trim system may also provide maximum upward tilt movement to place the motor in a trailering position of a separate power system exclusively for tilting the motor to the trailering position may be utilized. U.S. patent application Ser. No. 181,685, filed Apr. 14, 1988, and entitled "Combined Trim, Tilt and Lift Apparatus for a Marine Propulsion Device", which is assigned to the assignee of this application, discloses an outboard motor transom extension mounting assembly comprising a quadrilateral linkage arrangement and utilizing separate hydraulic power means to effect vertical lift, trim and tilt movement to the motor. Such separate lift, trim and tilt systems are generally independently operable and manual adjustment of each of them by the boat operator to obtain optimum drive unit positioning is somewhat difficult and requires a fairly substantial level of operating skill. For example, substantially varying drive unit positions, both in terms of lift position and trim position, are required for trolling or shallow water operation, acceleration to cruising, and on-plane operation at cruising speed.
U.S. patent application Ser. No. 092,168, filed Sept. 2, 1987, entitled "Automatic Engine Lift for Outboard Motors," and Ser. No. 172,399, filed Mar. 24, 1988, entitled "Position Control System for a Marine Propulsion Device", both of which are also assigned to the assignee of this application, disclose means for controlling the movement and positioning of transom extension mounted outboard motors to avoid hazardous or undesirable operating conditions. The disclosed control systems operate automatically to lift or lower the motor with respect to the motor transom until the hazard or undesirable condition is eliminated.
U.S. Pat. No. 4,318,699 discloses a system for automatically trimming a marine drive unit in response to a sensed operating condition, such as engine speed, or on-plane and off-plane operation of the boat. The drive is typically trimmed out at high speeds and trimmed in at lower speeds. The system of the foregoing patent is automatically responsive to move the drive unit to preselected trim positions characteristic of the boat on which it is used.
U.S. Pat. No. 4,718,872 describes a system for automatically adjusting the trim of a marine drive unit by sensing an increase in boat speed and adjusting the trim until the boat speed ceases to increase. The automatic control system is operative to incrementally trim the drive unit in one direction as long as the movement results in an increase in speed and then to trim the drive unit in the opposite direction as long as the adjustment results in an increase in speed.
Although proper trim control has a significant impact on efficient operation of the drive unit, whether for slow speed trolling, acceleration, or high speed cruising, the vertical lift position of the drive unit also has a significant effect on operation in any of these various modes, as indicated previously. The use of engine lift, as well as trim, to optimize performance in various operating modes has substantially increased the complexity of adjustment for the boat operator. As a result, the casual boater will usually not be able to achieve the best overall operating position or will not desire to take the time to achieve it, particularly where frequent changes in operating modes are required.
It would be desirable, therefore, to be able to reposition a marine drive unit at a position defined by a previously determined set of lift and trim positions for each of various boat operating modes. Further, it would be desirable to be able to reset the lift and trim positions based on changes in various boat operating conditions.